Abdomen: Topographic Anatomy

Abdomen > Topographic Anatomy > Study Aims
STUDY AIMS
At the end of your study, you should be able to:
Understand the boundaries of the abdominal cavity
Identify surface landmarks of the abdomen
Know the four quadrants of the abdomen and their contents
Know the nine regions of the abdomen
Know the lines and planes that create the four quadrants and nine regions

Abdomen > Topographic Anatomy > Guides
GUIDE

4-1: Abdomen: Topographic Anatomy
    Abdomen: General description
  • Lies between the diaphragm and the pelvic inlet.
  • Is the largest cavity in the body and is continuous with the pelvic cavity.
  • Lined with parietal peritoneum, a serous membrane
  • Bounded superiorly by the diaphragm
    • Has a concave dome
    • Spleen, liver, part of the stomach, and part of the kidneys lies under the dome and are protected by the lower ribs and costal cartilages.
  • Lower extent lies in the greater pelvis
    • Between the ala or wings of the ilia
    • Ileum, cecum, and sigmoid colon thus partly protected
  • Anterior and lateral walls composed of muscle
    • Viscera in these areas are more likely to be damaged by blunt force and penetrating injuries.
  • Posterior wall comprised of vertebral column, the lower ribs, and associated muscles
    • Protect the abdominal contents.
    Bony landmarks of the abdomen (Plate 248)
  • Xiphoid process
  • Lower six costal cartilages
  • Anterior ends of the lower six ribs (ribs 7 to 12) (Section 3-3: ThoraxBody Wall)
  • Lumbar vertebrae (L1 to L5)
  • Pelvis
    • Iliac crest
    • Anterior superior iliac spine (ASIS)
    • Anterior inferior iliac spine
    • Pubic symphysis
    • Pubic crest and pubic tubercle
    Abdomen: Topographical anatomy (Plate 247) (Table 4-1-1)
  • Costal margin: Formed by the medial borders of the 7th through 10th costal cartilages
  • Rectus sheath
    • From xiphoid process and 5th through 7th costal cartilages → pubic symphysis and pubic crest
    • Contains rectus abdominis muscle (Section 4-2: AbdomenBody Wall)
  • Linea alba
    • A slight indentation that can sometimes be seen extending from the xiphoid process to the pubic symphysis
    • A fibrous raphe where the aponeuroses of the external and internal abdominal oblique and the transversus abdominis muscles on either side unite.
  • Semilunar line (linea semilunaris)
    • Vertical indentation seen as a curved line from the tip of the ninth rib cartilage to the pubic tubercle on each side in well-muscled individuals
    • Represents the lateral edge of the rectus abdominus muscle
  • Tendinous intersections
    • Transverse attachments between the anterior rectus sheath and rectus abdominis muscle
    • May be seen as transverse grooves in skin on either side of midline (six-pack)
  • Inguinal ligament
    • From ASIS to pubic tubercle of pelvis
    • Folded inferior edge of external abdominal aponeurosis
    • Separates abdominal region from thigh
  • Umbilicus
    • At approximate level of intervertebral disc between the L3 and L4
    • Marks the T10 dermatome
  • Liver (Plate 286)
    • Mainly in the right upper quadrant, behind ribs 7 through 11 on the right side
    • Crosses the midline to reach towards the left nipple (Section 4-5: AbdomenViscera (Accessory Organs))
  • Spleen
    • Beneath ribs 9 through 11 on the left side
    • 10th rib is axis of spleen
  • Kidneys
    • Located in loin region
    • Left kidney is higher than right (pelvis at L1/2 on left and L2/3 on right) (Section 4-8: AbdomenKidneys and Suprarenal Glands)
    Abdominal contents (Fig. 4-1-1)
  • Gastrointestinal tract
    • Stomach
    • Duodenum
    • Ileum
    • Jejunum
    • Cecum and appendix
    • Ascending, transverse and descending colon
    • Part of the sigmoid colon
  • Accessory digestive organs
    • Liver
    • Gallbladder
    • Pancreas
  • Spleen
  • Suprarenal glands
  • Urinary system—kidneys and ureters
    • Kidneys are the only organs developing beneath the parietal peritoneum
    • Never have a mesentery
    • Thus are primarily retroperitoneal
  • Organs that develop within the abdominal cavity and then become retroperitoneal
    • Are called secondarily retroperitoneal
    • Pancreas
    • Two thirds of the duodenum
    • Ascending and descending colon.
  • All the rest of the organs are peritoneal
    • Lie within the peritoneal cavity
    • Covered by a layer of visceral peritoneum
    • Visceral peritoneum is continuous with the parietal peritoneum lining the cavity via a mesentery.
    Abdominal regions (Plate 268)
  • Abdominal quadrants
    • Clinicians usually divide the abdomen is into four quadrants for descriptive purposes, using the following planes:
      • Median plane: imaginary vertical line following the line alba from the xiphoid process to the pubic symphysis
      • Transumbilical plane: imaginary horizontal line at the level of the umbilicus
    • These lines or planes create four quadrants (Table 4-1-2)
      • Right upper
      • Left upper
      • Right lower
      • Left lower
  • Abdominal regions
    • Clinicians may divide the abdomen into nine regions
      • For more accurate descriptive and diagnostic purposes
      • Use two vertical and three horizontal lines or planes
    • Horizontal planes (in descending order):
      • Subcostal plane: passes through the lower border of the 10th costal cartilage on either side
      • Sometimes the transpyloric plane is used instead of the subcostal; passes through the pylorus on the right and the tips of the ninth costal cartilage on either side)
      • Transumbilical plane: passes through the umbilicus at the level of the L3/4 intervertebral disc
      • Transtubercular (intertubercular) plane: passes through the tubercles of the iliac crests and the body of L5
    • Vertical planes
      • Right midclavicular line
      • Left midclavicular line
      • Pass from the midpoint of the clavicle to the midpoint of inguinal ligament.
    • These planes create nine abdominal regions: (Plate 268)
      • Right and left hypochondriac regions, superiorly on either side
      • Right and left lumbar (flank) regions, centrally on either side
      • Right and left inguinal (groin) regions, inferiorly on either side
      • Epigastric region superiorly and centrally
      • Umbilical region, with the umbilicus as its center
      • Hypogastric or suprapubic region, inferiorly and centrally
  • Descriptive quadrants and regions are essential in clinical practice
    • Each area represents certain visceral structures
    • Allow correlation of pain and referred pain from these areas to specific organs.
  • Regions and quadrants are palpated, percussed, and auscultated during clinical examination
Abdomen > Topographic Anatomy > Figures
FIGURES
Plate 247: Abdomen—Topographic Anatomy
Plate 268: Abdomen—Peritoneal Cavity—Regions and Planes of the Abdomen
Fig. 4-1-1: Solid abdominal organs in situ. (From Moses KP, Banks JC, Nava PB, et al. Atlas of Clinical Gross Anatomy. Mosby, 2005. P. 386, Fig. 33.1)
Abdomen > Topographic Anatomy > Tables
TABLES

Table 4-1-1: Muscles of the anterolateral abdominal wall
Name of muscle
(nerve supply)
Origin Insertion Action
External oblique
(T5-T12 spinal nerves)
External surface of ribs 5-12 Becomes aponeurotic and attaches to the xiphoid process, linea alba, pubic crest, pubic tubercle, and anterior half of iliac crest Fixes and rotates trunk, pulls down ribs in forced expiration
Internal oblique (spinal nerves T6-T12, iliohypogastric and ilioinguinal nerves) Thoracolumbar fascia anterior two-thirds of iliac crest, lateral half of inguinal ligament Inferior border of ribs 10-12 and their costal cartilages, pubic crest and pectin pubis via conjoint tendon with transversus Assists in flexing and rotating trunk; pulls down ribs in forced expiration
Transversus abdominis (spinal nerves T5-T12, iliohypogastric and ilioinguinal nerves) Internal surface of lower six costal cartilages, thoracolumbar fascia, iliac crest, lateral third of inguinal liagement Pubic crest, linea alba, symphysis pubis; forms conjoint tendon to pectus pubis with internal oblique Compresses and supports abdominal contents and flexes external and internal oblique muscles
Rectus abdominis (spinal nerves T6-T12) Symphysis pubis and pubic crest Costal cartilages 5-7 and xiphoid process Compresses abdominal contents and flexes trunk (lumbar vertebrae)
(From Granger, NA. Crash Course Anatomy, 3rd edition. Mosby, 2007. Fig. 5.4. [Currently in production])

Table 4-1-2: Contents of the Abdominal Quadrants
RIGHT UPPER QUADRANT (RUQ) LEFT UPPER QUADRANT (LUQ)
 •  Liver (right lobe)
 •  Gallbladder
 •  Pylorus (of stomach)
 •  Duodenum (parts 1 through 3)
 •  Pancreas (head)
 •  Right kidney and suprarenal gland
 •  Colon: distal ascending colon, hepatic flexure and right half of transverse colon
 •  Liver (left lobe)
 •  Spleen
 •  Stomach
 •  Jejunum and proximal ileum
 •  Pancreas (body and tail)
 •  Left kidney and suprarenal gland
 •  Colon: left half of transverse colon, splenic flexure and superior part of descending colon
RIGHT LOWER QUADRANT (RLQ) LEFT LOWER QUADRANT (LLQ)
 •  Majority of ileum
 •  Cecum with vermiform appendix
 •  Proximal ascending colon
 •  Proximal right ureter
 •  Distal descending colon
 •  Sigmoid colon
 •  Left ureter
 •  Ovaries
 •  Uterine tubes
 •  Right and left ductus deferens
 •  Uterus (if enlarged)
 •  Urinary bladder (if full, especially in women)

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